Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Curranm on February 25, 2020, 03:29:02 pm

Title: plexi 50 modification question.
Post by: Curranm on February 25, 2020, 03:29:02 pm

I am going to build a hoffman 50 with the hot switch on a relay. At the 470K/470K voltage divider going into the next tube stage after the relay I w9ould like to put in another Volume/gain control. So I was going to replace the 470K to ground with a 500kA or 1MA pot. is the right spot for something like that? Everything else about the schematic will stay the same. just curious! thanks in advance for your help!

Title: Re: plexi 50 modification question.
Post by: PRR on February 25, 2020, 04:17:24 pm

Sounds like a good plan.

Title: Re: plexi 50 modification question.
Post by: shooter on February 25, 2020, 05:10:17 pm

Quote

I am going to build a hoffman 50 with the hot switch

I attached Dougs version, He re-purposes the 2nd input so there isn't any 470k voltage divider. 
Are you doing something different than His intent?

Title: Re: plexi 50 modification question.
Post by: shooter on February 25, 2020, 05:55:14 pm

 :think1:
missed 12b

Title: Re: plexi 50 modification question.
Post by: Curranm on February 27, 2020, 08:50:16 am

I am not really trying to break away from the 50 hotswitch plexi, BUT I have built one of these before AND I want to make the switched in stage a bit more fun and controllable with the added gain control. that is really where my noodle is at.

Title: Re: plexi 50 modification question.
Post by: sluckey on February 27, 2020, 10:03:25 am

Just replace R12b with a 500K pot. One leg to ground, one leg to C3, and the wiper to the switch.